1. Field of the Invention
This invention pertains to the construction of a water or fluid cooled door for a blender with a specific control of door size to provide a gap between the door and the blender housing together with a tapered edge construction. More particularly the design results in minimum pressure contact with adjacent support structure. The door design results in little or no continuous build-up of even sticky natured matrix materials, especially sticky wood particles. The cooling water, at a typical 40-50 degrees F., causes a water condensate to form on the door surface and edges. The water condensate often comes from the warm moisture laden air inside the blender. The layer of water condensate prevents sticking of the resin coated particles on the surface and edges of the door. The door remains operable over a sustained period of time without involuntary or unscheduled shut-down requirement. Product quality is improved. Blender operation time between scheduled maintenance down-time is greatly increased.
2. Description of the Prior Art
Prior art apparatus are well known for applying liquid or powdered resins to plastics, wood particles, or other matrix materials. Shaft and vessel walls are typically water cooled.
The exit door is typically not cooled but is coated with a plastic coating. The plastic material does not withstand the constant wear and abrasion where all the material passes out the exit of the blender across the surface of the exit door. The plastic wears through or is lifted up by the particles of the matrix, i.e., wood particles.
A major manufacturer typically constructs a riveted frame of metal "like a picture frame" around the plastic material of the door in order to keep the plastic in place.
The construction of the dry metal frame compounds the problem of matrix material build-up, i.e., wood particles, on the door surface and edges. The metal frame edges form another means, actually an easier means for the ready opportunity of build-up of matrix material onto the door.
The typical door construction and modifications in the prior art illustrates the complete misunderstanding of the real problem in product mixing.
Such prior art solutions as placing a metal frame around the door allows the door to remain intact for a longer period, but at the expense of (1) Faster material build-up, (2) Reduced quality of product, (3) poor door operation (or typically the door may become jammed partially open), (4) Immediate nonscheduled shut-down is necessary.
The current exit door construction in blenders (i.e. particle-board) results in numerous disadvantages:
1. The tight fitting edge of the door presses the sticky matrix clinging to the edge. This condition presents a constant problem in operating the door. There is insufficient door clearance. Usually, the door will become jammed in place.
2. A jammed door almost closed will cause overload amperage on the motor; the panel breakers will overload and the blender will be shut down. The entire production line will have to stop while the door is being cleaned.
3. A jammed door partially open will remain in one position. This is often the case.
4. An operator will wire a door to its full open position.
5. A door will be removed completely.
6. Constant wear on the dry metal surface of the door and on the plastic cover added by some manufacturers to the door to prevent sticking will cause the plastic to lift off or wear away completely. The exposed dry metal leads to material buildup.
7. The resin and wood chip mixture can become very hard. These hard pieces can fall away, often in relatively large sizes and can cause harm in forming teeth in subsequent processing equipment or can cause difficulty in the board product itself.
8. Hard resin deposits in the board cause resin spots on board edges or on the surface.
9. Hard resin deposits often fall out of the board and cause cavities in the board edges or surface. The typical present exit door construction has been in effect for a number of years without an attempt to solve the problem of material buildup.
Some particleboard plants are now using a pressure control on the door, pressure related to the amperage load on the motor. A specific amperage load is maintained to keep the blender "working", i.e., greater energy level of mixing.
The increased pressure of the door closing mechanism again adds to the problem because now the sticky matrix is pressed in place "balled up", as in the making of a "snow ball" effect. The build-up continues until the door is inoperable. Or the material which is now built up on the "picture frame" will fall off into the product mixture. As a result the hard now silhouetted "pieces of matching picture frame" are now loose in the product mixture to cause harm in machine teeth in subsequent operations or forming and in the product itself.